How to tell if an exoplanet is habitable

This composite image shows an exoplanet (the red spot) orbiting the brown dwarf 2M1207. This is the first exoplanet directly imaged. Image: ESO/Chauvin et al.

Figuring out whether a planet is habitable will take more than just understanding its orbit. According to a new study in the journal Science, scientists will also need to study a world’s atmosphere, magnetic field and even geological composition in order to really know if it’s capable of hosting life.

The big picture: Researchers have been hunting for habitable exoplanets using space and ground-based telescopes for years, but assessing whether a world can support life or not is difficult.

What they are looking for:

Considerable time is spent focusing on whether a planet is in its star’s “habitable zone” — an orbit in which liquid water can be sustained on the surface — but that alone can’t predict whether life will exist.

“To focus the search for extraterrestrial life, scientists must assess which features of Earth are essential to the development and sustenance of life for billions of years and whether the formation of such planets is common,” the study says.

Details: While understanding an exoplanet’s atmosphere is a good way to start a hunt for life, scientists will also need to learn more about a planet’s composition to see if it’s Earth-like.

“The heart of habitability lies in the planetary interior,” the study says.

If a world’s core is liquid iron like Earth’s, it could produce a sufficiently strong magnetic field to shield its surface from incoming harmful radiation, protecting water and possible life on its surface.

Even plate tectonics have bearing on habitability because the cycling of a planet’s crust helps control its climate, the study notes.

“By having these different variables, we can say this is the most likely — of all the planets that have been found — this one is the most likely to be habitable or to be most Earth-like,” study co-author Anat Shahar of the Carnegie Institution for Science told Axios.

What’s next: Although scientists have discovered thousands of exoplanets so far, very few of them are thought to be potentially habitable. However, as more powerful telescopes come online, researchers should gain a better understanding of what secrets these planets may be hiding.